A. Field of the Invention
The present invention relates to a stator blade of a stator which is disposed between an impeller and a turbine in a torque converter.
B. Description of the Background Art
A torque converter is a device which includes an impeller, a turbine and a stator, and transmits torque through a working fluid which fills the inner spaces defined within the torque convertor. In an outer peripheral portion of the torque converter, the working fluid flows from the impeller to turbine, and in an inner peripheral portion of the torque converter the working fluid flows from the turbine to the impeller through the stator.
The stator is a member disposed between the impeller and the turbine, and is fixed to a stator shaft via a one-way clutch. The stator shaft is typically engaged with a fixed, non-rotating portion of a transmission housing. The stator is typically made of molded resin, aluminum alloy or the like, and is basically formed with an annular shell, an annular core and stator blades which extend between the shell and the core. The stator blades are disposed at circumferentially spaced positions, respectively, and extend from the shell at the radially inner position to the core at the radially outer position for the purpose of, e.g., controlling a direction of the working fluid returning from the turbine toward the impeller.
During idling of a vehicle provided with the torque converter, the impeller coupled to a crank shaft of an engine continuously rotates while rotation of the turbine is being restricted. Even during idling, therefore, the engine operates under a load, which increases a fuel consumption.
The fuel consumption can be improved by lowering a capacity coefficient (Cf) during idling, i.e., when a speed ratio (e) at a rotation speed (Ni) of the impeller to a rotation speed (No) of the turbine is 0. The capacity coefficient (Cf) is obtained by dividing the torque (Ti) of the impeller by the square of the rotation speed (Ni) of the impeller. If the capacity coefficient (Cf) is low, only a small energy is required for rotating the impeller during idling so that the fuel consumption of the vehicle during idling is improved.